The prior art cited in EP 0810025 A1 is considered as the closest known technique.
In fact, the present invention refers to the sector of devices for micronizing fluids, particularly flowable materials containing particles in the liquid state, agglomerates or fibres, that is, products that are substantially liquid and insoluble, but subject to the formation of portions that are solid or in any case, of different densities.
The homogenizing/micronizing apparatus (hereinafter, the terms homogenization and micronization, and other forms thereof, shall be used as synonyms) normally comprises a pump, possibly a high-pressure variable flow pump and a homogenizing valve, having an inlet connected to the delivery of the pump so as to receive the pressurized fluid and an outlet for the homogenized fluid under low pressure.
The micronization to be achieved essentially consists in the breaking down of said particles for the purpose of minimizing the size thereof and rendering the size uniform.
To reach this aim, the fluid is passed through a forced passage, of reduced size, from a first high-pressure chamber (connected to the delivery of the pump) to a second micronizing chamber (connected to the valve outlet).
This passage is defined by a passage head that is solidly constrained (and thus fixed) to a valve body and through which the fluid passes, and by an impact head that is axially movable with respect to the passage head. Specifically, the passage consists in a gap defined between the impact head and the small passage head.
The fluid under high pressure in the first chamber presses on a surface of the impact head, exerting a pressure on it that tends to widen the passage. A pusher is applied to the impact head and it exerts a force on the impact head in an axial direction, so as to oppose the pressure of the fluid.
In this manner, by suitably managing the action of the pusher, it is possible to maintain the breadth of the passage at a desired value that is substantially constant and that can be adjusted in any case. This force should be determined based on the operating flow rate and pressure levels of the homogenizing apparatus.
Therefore, as it flows through said forced passage from the first to the second chamber, the fluid undergoes a drop in pressure, while at the same time it is also accelerated according to the equation of energy conservation. This acceleration leads to a breaking down of the particles of the fluid. Moreover, an impact ring has been known to be arranged in the second chamber so as to intercept the accelerated fluid; in this manner, the fluid strikes against the impact ring at high velocity and this constitutes a further contribution to the breaking up of the particles. The impact ring also protects the chamber in which the impact takes place from wear.
In general, one wants to optimize the energy employed in the homogenization process, that is, with the energy applied to the fluid being equal, one wants to obtain the best possible result for the homogenization of the fluid, in the terms described above, or with the results being the same, one attempts to decrease the energy (pressure) employed.
In the prior art described hereinabove, the product substantially passes through a toroid that tends to widen (cf. FIGS. 1 and 2 of the prior art) and the homogenizing effect is provided by the increased cutting force that the product encounters as it passes from the central channel onwards out of the toroid.
However, much energy is uselessly wasted in the homogenization and micronization step and converted into heat, which is the cause of the intrinsic inefficiency of high-pressure homogenizing apparatuses.
EP 0850683 A1 discloses a fine particle production device, wherein, according to the third embodiment illustrated therein, a pre-treatment unit has been added between the high pressure pump and the fine particle production device. Said third embodiment needs to be integrated or associated with the main device or first embodiment (a system with a fixed geometry and a constant shear rate, which is quite different from the aims of the present invention) and it cannot be used as a stand-alone device.
US 2004/160855 discloses a homogenizing apparatus comprising an inlet for a pressurized fluid, a homogenization zone, an outlet for the fluid at a lower pressure, wherein in the homogenization zone the fluid passes from a zone having a large diameter to a zone having a smaller diameter. The homogenization zone comprises an interacting element shared by a first stage, equipped with a first deflector plug, and a second stage for creating back pressure having a second deflector plug.
However said apparatus lacks efficiency and the deflector plugs are not adjustable independently.